/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
 * scalbln(double x, long n)
 * scalbln(x,n) returns x * 2**n computed by exponent
 * manipulation rather than by actually performing an
 * exponentiation or a multiplication.
 */

#include "math_libm.h"
#include "math_private.h"
#include <limits.h>

#ifdef __WATCOMC__ /* Watcom defines huge=__huge */
#undef huge
#endif

static const double
two54  = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
huge   = 1.0e+300,
tiny   = 1.0e-300;

double scalbln(double x, long n)
{
    int32_t k, hx, lx;

    EXTRACT_WORDS(hx, lx, x);
    k = (hx & 0x7ff00000) >> 20; /* extract exponent */
    if(k == 0) {  /* 0 or subnormal x */
        if((lx | (hx & 0x7fffffff)) == 0) {
            return x;  /* +-0 */
        }
        x *= two54;
        GET_HIGH_WORD(hx, x);
        k = ((hx & 0x7ff00000) >> 20) - 54;
    }
    if(k == 0x7ff) {
        return x + x;  /* NaN or Inf */
    }
    k = (int32_t)(k + n);
    if(k > 0x7fe) {
        return huge * copysign(huge, x);  /* overflow */
    }
    if(n < -50000) {
        return tiny * copysign(tiny, x);  /* underflow */
    }
    if(k > 0) {  /* normal result */
        SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
        return x;
    }
    if(k <= -54) {
        if(n > 50000) { /* in case integer overflow in n+k */
            return huge * copysign(huge, x);  /* overflow */
        }
        return tiny * copysign(tiny, x); /* underflow */
    }
    k += 54; /* subnormal result */
    SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
    return x * twom54;
}
libm_hidden_def(scalbln)


double scalbn(double x, int n)
{
    return scalbln(x, n);
}
libm_hidden_def(scalbn)
